1. Field of the Invention
The present invention relates to a method for magnetic orientation of magnetic recording media such a magnetic disk, a magnetic tape and the like, and a system for such magnetic orientation, and more particularly, to a method for magnetic orientation of magnetic recording media which are suitable for high density recording and a system therefor and an inside magnetic recording medium.
2. Description of the Related Art
Prior techniques for magnetic orientation of high density magnetic recording mediums include disposing a plurality of electromagnets or permanent magnets both above and below the magnetic recording medium, as described, for example, in U.S. Pat. No. 4,189,508, Japanese Patent Kokai (Laid-open) No. 62-24430 and Japanese Patent Kokoku (Post-Exam. Publn.) No. 62-50888. Strict control of the relative positions of a plurality of magnets and the distances between the magnets and the magnetic recording medium (U.S. Pat. No. 4,189,508) or a combination of a plurality of DC magnets or permanent magnets and AC magnets (Japanese Patent Kokai No. 62-24430) have been proposed.
The aforementioned prior techniques have not been designed to provide a satisfactorily high ratio of reproducing output signal to noise (S/N) and have disadvantages that they are incapable of producing a magnetic recording medium having a high output and a high ratio of S/N. An explanation about one of the causes of this problem may be as follows. In order to enhance the reproducing output of the magnetic recording medium, an increase of residual flux density is generally required and for this purpose one known method is to increase the thickness of magnetic coating film. On the other hand, it is known that if the film thickness is increased, the properties at higher frequencies become poor.
In order to maintain better properties at higher frequencies, therefore, an attempt has been made to orient magnetic particles in a magnetic field so that the ratio of S/N is increased with the film thickness being kept thin.
However, this conventional technique could not achieve a desired reduction of noise (N), though the output (S) was increased. This is attributed to occurrence of the coagulation of magnetic particles.
Therefore, there has been a problem that the prior art is unable to produce a magnetic recording medium having a high output and a high S/N ratio.